Recent development and adaptation of optical techniques for applications to communications, data processing, and similar transmission systems has numerous advantages as compared with electronic systems which have comparable functional objectives.
Low-loss, high quality, multi-mode fiber optic cable has been developed which renders optical communication, data processing, and signal transmission systems feasible, practical, and desirable. Some of the advantages of fiber optic cables used in such systems include greatly reduced size, weight, and cost; electrical isolation which eliminates grounding and ground loops; reduced constraints relative to impedance matching; and, easy coupling to common logic circuitry by use of available light sources and detectors. Moreover, fiber optic cables permit high channel isolation, easy interchangeability with electrical cable, and greatly reduced electromagnetic interference.
One of the most important advantages offered by fiber optic cables in military use is their characteristic immunity to radio frequency signals and the fact that the transmitted light signals are contained wholly within the cables. In ground communication systems, this obviously greatly increases transmission security. The use of optical cables also eliminates cross talk and optical paths provided by such fiber optic cables are resistant to electromagnetic interference from other equipment on air craft, vessel, or vehicle and even immune to electromagnetic pulses, such as may be generated by nuclear explosions.
In such optical systems, there is a need for optical couplers which are connectable to fiber optic cables, for example, to provide the capability of intercepting and extracting signal information from an optical path, as well as introducing signal information into that optical path.
Additionally, it is desirable that such a coupler be selectively operable to redirect light energy signals into or out of the optical path as desired and, in such selective operation, be remotely controllable if desired.